Because GitLab couldn't be bothered to be a great, reliable, focused, self-hosted code development and CI/CD solution. They had to tack on half-baked copies of every dev tool in existence.
They are a great reliable pretty focused self-hostable dev/devops platform with a lot of trendy shit as extra. Most of which you get for free... they executed the open core model as well as possible (in this sector).
What do you think they should have done better that would have helped them (their bottom line, growth, brand, sustainability, or some combination of these)?